Underlying mechanisms of impaired visceral pain perception in older people.

There is increasing recognition that aging can have a profound effect on the presentation of illness. Older patients with diseases of visceral organs are much more likely than younger adults to present atypically. Examples are the frequent absence of pain in older patients with conditions such as myocardial infarction, peptic ulcer disease, and pneumothorax. Recent developments have helped elucidate the complex processes involved in signaling information from the effects of noxious stimuli on visceral organs, but understanding of why older patients with visceral disease are more likely to present without pain is still rudimentary. Much of the previous experimental evidence on age-related differences relates to somatic rather than visceral sources of pain. As a result, it may not have direct comparability with transmission of information on visceral damage or noxious stimulation. This article reviews the published pathophysiological data on sensory transmission from visceral organs. Where possible, this is correlated with other published clinical studies on age-related differences in visceral pain perception. Areas in which experimental evidence is absent are also highlighted. Finally suggestions are made as to how newer experimental and neuroimaging techniques may help to increase understanding of this complex subject and its resulting clinical applicability.